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Commit 46392dc0 authored by Neil Fuller's avatar Neil Fuller
Browse files

Extract an interface for ServiceConfigAccessor 

This is a simple refactoring before later commits where it will be
beneficial to have an interface for testing.

This mirrors the situation in com.android.server.timezonedetector and is
part of a sequence of changes to make com.android.server.timedetector
follow the patterns for configuration used there.

Bug: 172891783
Bug: 229740080
Test: Build only
Change-Id: If2cb5468c5899b85cfe31522ebdba8517e9e359a
parent 4a56099b

services/core/java/com/android/server/timedetector/ServiceConfigAccessor.java

+25 −188
Original line number Diff line number Diff line
@@ -15,214 +15,51 @@ 
 */

package com.android.server.timedetector;



import static com.android.server.timedetector.ServerFlags.KEY_TIME_DETECTOR_LOWER_BOUND_MILLIS_OVERRIDE;

import static com.android.server.timedetector.ServerFlags.KEY_TIME_DETECTOR_ORIGIN_PRIORITIES_OVERRIDE;

import static com.android.server.timedetector.TimeDetectorStrategy.ORIGIN_NETWORK;

import static com.android.server.timedetector.TimeDetectorStrategy.ORIGIN_TELEPHONY;



import android.annotation.NonNull;

import android.annotation.Nullable;

import android.content.Context;

import android.os.Build;

import android.os.SystemProperties;



import com.android.internal.R;

import com.android.internal.annotations.GuardedBy;

import com.android.internal.util.Preconditions;

import com.android.server.timedetector.TimeDetectorStrategy.Origin;

import com.android.server.timezonedetector.ConfigurationChangeListener;



import java.time.Instant;

import java.util.Arrays;

import java.util.Objects;

import java.util.Optional;

import java.util.Set;

import java.util.function.Supplier;



/**

 * A singleton that provides access to service configuration for time detection. This hides how

 * configuration is split between static, compile-time config and dynamic, server-pushed flags. It

 * provides a rudimentary mechanism to signal when values have changed.

 */

final class ServiceConfigAccessor {



    private static final int SYSTEM_CLOCK_UPDATE_THRESHOLD_MILLIS_DEFAULT = 2 * 1000;



    /**

     * By default telephony and network only suggestions are accepted and telephony takes

     * precedence over network.

     */

    private static final @Origin int[]

            DEFAULT_AUTOMATIC_TIME_ORIGIN_PRIORITIES = { ORIGIN_TELEPHONY, ORIGIN_NETWORK };



/**

     * Time in the past. If an automatic time suggestion is before this point, it is sure to be

     * incorrect.

     */

    private static final Instant TIME_LOWER_BOUND_DEFAULT = Instant.ofEpochMilli(

            Long.max(android.os.Environment.getRootDirectory().lastModified(), Build.TIME));



    /** Device config keys that affect the {@link TimeDetectorService}. */

    private static final Set<String> SERVER_FLAGS_KEYS_TO_WATCH = Set.of(

            KEY_TIME_DETECTOR_LOWER_BOUND_MILLIS_OVERRIDE,

            KEY_TIME_DETECTOR_ORIGIN_PRIORITIES_OVERRIDE

    );



    private static final Object SLOCK = new Object();



    /** The singleton instance. Initialized once in {@link #getInstance(Context)}. */

    @GuardedBy("SLOCK")

    @Nullable

    private static ServiceConfigAccessor sInstance;



    @NonNull private final Context mContext;

    @NonNull private final ConfigOriginPrioritiesSupplier mConfigOriginPrioritiesSupplier;

    @NonNull private final ServerFlagsOriginPrioritiesSupplier mServerFlagsOriginPrioritiesSupplier;

    @NonNull private final ServerFlags mServerFlags;



    /**

     * If a newly calculated system clock time and the current system clock time differs by this or

     * more the system clock will actually be updated. Used to prevent the system clock being set

     * for only minor differences.

 * An interface that provides access to service configuration for time detection. This hides

 * how configuration is split between static, compile-time config, dynamic server-pushed flags and

 * user settings. It provides listeners to signal when values that affect different components have

 * changed.

 */

    private final int mSystemClockUpdateThresholdMillis;



    private ServiceConfigAccessor(@NonNull Context context) {

        mContext = Objects.requireNonNull(context);

        mServerFlags = ServerFlags.getInstance(mContext);

        mConfigOriginPrioritiesSupplier = new ConfigOriginPrioritiesSupplier(context);

        mServerFlagsOriginPrioritiesSupplier =

                new ServerFlagsOriginPrioritiesSupplier(mServerFlags);

        mSystemClockUpdateThresholdMillis =

                SystemProperties.getInt("ro.sys.time_detector_update_diff",

                        SYSTEM_CLOCK_UPDATE_THRESHOLD_MILLIS_DEFAULT);

    }



    /** Returns the singleton instance. */

    static ServiceConfigAccessor getInstance(Context context) {

        synchronized (SLOCK) {

            if (sInstance == null) {

                sInstance = new ServiceConfigAccessor(context);

            }

            return sInstance;

        }

    }

public interface ServiceConfigAccessor {



    /**

     * Adds a listener that will be called when server flags related to this class change. The

     * callbacks are delivered on the main looper thread.

     * Adds a listener that will be invoked when {@link ConfigurationInternal} may have changed.

     * The listener is invoked on the main thread.

     *

     *

     * <p>Note: Only for use by long-lived objects. There is deliberately no associated remove

     * method.

     */

    void addListener(@NonNull ConfigurationChangeListener listener) {

        mServerFlags.addListener(listener, SERVER_FLAGS_KEYS_TO_WATCH);

    }



    @NonNull

    @Origin int[] getOriginPriorities() {

        int[] serverFlagsValue = mServerFlagsOriginPrioritiesSupplier.get();

        if (serverFlagsValue != null) {

            return serverFlagsValue;

        }



        int[] configValue = mConfigOriginPrioritiesSupplier.get();

        if (configValue != null) {

            return configValue;

        }

        return DEFAULT_AUTOMATIC_TIME_ORIGIN_PRIORITIES;

    }



    int systemClockUpdateThresholdMillis() {

        return mSystemClockUpdateThresholdMillis;

    }



    @NonNull

    Instant autoTimeLowerBound() {

        return mServerFlags.getOptionalInstant(KEY_TIME_DETECTOR_LOWER_BOUND_MILLIS_OVERRIDE)

                .orElse(TIME_LOWER_BOUND_DEFAULT);

    }

    void addListener(@NonNull ConfigurationChangeListener listener);



    /**

     * A base supplier of an array of time origin integers in priority order.

     * It handles memoization of the result to avoid repeated string parsing when nothing has

     * changed.

     * Returns the absolute threshold below which the system clock need not be updated. i.e. if

     * setting the system clock would adjust it by less than this (either backwards or forwards)

     * then it need not be set.

     */

    private abstract static class BaseOriginPrioritiesSupplier implements Supplier<@Origin int[]> {

        @GuardedBy("this") @Nullable private String[] mLastPriorityStrings;

        @GuardedBy("this") @Nullable private int[] mLastPriorityInts;



        /** Returns an array of {@code ORIGIN_*} values, or {@code null}. */

        @Override

        @Nullable

        public @Origin int[] get() {

            String[] priorityStrings = lookupPriorityStrings();

            synchronized (this) {

                if (Arrays.equals(mLastPriorityStrings, priorityStrings)) {

                    return mLastPriorityInts;

                }



                int[] priorityInts = null;

                if (priorityStrings != null && priorityStrings.length > 0) {

                    priorityInts = new int[priorityStrings.length];

                    try {

                        for (int i = 0; i < priorityInts.length; i++) {

                            String priorityString = priorityStrings[i];

                            Preconditions.checkArgument(priorityString != null);



                            priorityString = priorityString.trim();

                            priorityInts[i] = TimeDetectorStrategy.stringToOrigin(priorityString);

                        }

                    } catch (IllegalArgumentException e) {

                        // If any strings were bad and they were ignored then the semantics of the

                        // whole list could change, so return null.

                        priorityInts = null;

                    }

                }

                mLastPriorityStrings = priorityStrings;

                mLastPriorityInts = priorityInts;

                return priorityInts;

            }

        }



        @Nullable

        protected abstract String[] lookupPriorityStrings();

    }



    /** Supplies origin priorities from config_autoTimeSourcesPriority. */

    private static class ConfigOriginPrioritiesSupplier extends BaseOriginPrioritiesSupplier {



        @NonNull private final Context mContext;



        private ConfigOriginPrioritiesSupplier(Context context) {

            mContext = Objects.requireNonNull(context);

        }



        @Override

        @Nullable

        protected String[] lookupPriorityStrings() {

            return mContext.getResources().getStringArray(R.array.config_autoTimeSourcesPriority);

        }

    }

    int systemClockUpdateThresholdMillis();



    /**

     * Supplies origin priorities from device_config (server flags), see

     * {@link ServerFlags#KEY_TIME_DETECTOR_ORIGIN_PRIORITIES_OVERRIDE}.

     * Returns a lower bound for valid automatic times. It is guaranteed to be in the past,

     * i.e. it is unrelated to the current system clock time.

     * It holds no other meaning; it could be related to when the device system image was built,

     * or could be updated by a mainline module.

     */

    private static class ServerFlagsOriginPrioritiesSupplier extends BaseOriginPrioritiesSupplier {



        @NonNull private final ServerFlags mServerFlags;



        private ServerFlagsOriginPrioritiesSupplier(ServerFlags serverFlags) {

            mServerFlags = Objects.requireNonNull(serverFlags);

        }

    @NonNull

    Instant autoTimeLowerBound();



        @Override

        @Nullable

        protected String[] lookupPriorityStrings() {

            Optional<String[]> priorityStrings = mServerFlags.getOptionalStringArray(

                    KEY_TIME_DETECTOR_ORIGIN_PRIORITIES_OVERRIDE);

            return priorityStrings.orElse(null);

        }

    }

    /**

     * Returns the order to look at time suggestions when automatically detecting time.

     * See {@code #ORIGIN_} constants

     */

    @NonNull

    @Origin int[] getOriginPriorities();

}

services/core/java/com/android/server/timedetector/ServiceConfigAccessorImpl.java

0 → 100644
+229 −0
Original line number Diff line number Diff line 
/*

 * Copyright 2021 The Android Open Source Project

 *

 * Licensed under the Apache License, Version 2.0 (the "License");

 * you may not use this file except in compliance with the License.

 * You may obtain a copy of the License at

 *

 *      http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.android.server.timedetector;



import static com.android.server.timedetector.ServerFlags.KEY_TIME_DETECTOR_LOWER_BOUND_MILLIS_OVERRIDE;

import static com.android.server.timedetector.ServerFlags.KEY_TIME_DETECTOR_ORIGIN_PRIORITIES_OVERRIDE;

import static com.android.server.timedetector.TimeDetectorStrategy.ORIGIN_NETWORK;

import static com.android.server.timedetector.TimeDetectorStrategy.ORIGIN_TELEPHONY;



import android.annotation.NonNull;

import android.annotation.Nullable;

import android.content.Context;

import android.os.Build;

import android.os.SystemProperties;



import com.android.internal.R;

import com.android.internal.annotations.GuardedBy;

import com.android.internal.util.Preconditions;

import com.android.server.timedetector.TimeDetectorStrategy.Origin;

import com.android.server.timezonedetector.ConfigurationChangeListener;



import java.time.Instant;

import java.util.Arrays;

import java.util.Objects;

import java.util.Optional;

import java.util.Set;

import java.util.function.Supplier;



/**

 * A singleton implementation of {@link ServiceConfigAccessor}.

 */

final class ServiceConfigAccessorImpl implements ServiceConfigAccessor {



    private static final int SYSTEM_CLOCK_UPDATE_THRESHOLD_MILLIS_DEFAULT = 2 * 1000;



    /**

     * By default telephony and network only suggestions are accepted and telephony takes

     * precedence over network.

     */

    private static final @Origin int[]

            DEFAULT_AUTOMATIC_TIME_ORIGIN_PRIORITIES = { ORIGIN_TELEPHONY, ORIGIN_NETWORK };



    /**

     * Time in the past. If an automatic time suggestion is before this point, it is sure to be

     * incorrect.

     */

    private static final Instant TIME_LOWER_BOUND_DEFAULT = Instant.ofEpochMilli(

            Long.max(android.os.Environment.getRootDirectory().lastModified(), Build.TIME));



    /** Device config keys that affect the {@link TimeDetectorService}. */

    private static final Set<String> SERVER_FLAGS_KEYS_TO_WATCH = Set.of(

            KEY_TIME_DETECTOR_LOWER_BOUND_MILLIS_OVERRIDE,

            KEY_TIME_DETECTOR_ORIGIN_PRIORITIES_OVERRIDE

    );



    private static final Object SLOCK = new Object();



    /** The singleton instance. Initialized once in {@link #getInstance(Context)}. */

    @GuardedBy("SLOCK")

    @Nullable

    private static ServiceConfigAccessor sInstance;



    @NonNull private final Context mContext;

    @NonNull private final ServerFlags mServerFlags;

    @NonNull private final ConfigOriginPrioritiesSupplier mConfigOriginPrioritiesSupplier;

    @NonNull private final ServerFlagsOriginPrioritiesSupplier mServerFlagsOriginPrioritiesSupplier;



    /**

     * If a newly calculated system clock time and the current system clock time differs by this or

     * more the system clock will actually be updated. Used to prevent the system clock being set

     * for only minor differences.

     */

    private final int mSystemClockUpdateThresholdMillis;



    private ServiceConfigAccessorImpl(@NonNull Context context) {

        mContext = Objects.requireNonNull(context);

        mServerFlags = ServerFlags.getInstance(mContext);

        mConfigOriginPrioritiesSupplier = new ConfigOriginPrioritiesSupplier(context);

        mServerFlagsOriginPrioritiesSupplier =

                new ServerFlagsOriginPrioritiesSupplier(mServerFlags);

        mSystemClockUpdateThresholdMillis =

                SystemProperties.getInt("ro.sys.time_detector_update_diff",

                        SYSTEM_CLOCK_UPDATE_THRESHOLD_MILLIS_DEFAULT);

    }



    /** Returns the singleton instance. */

    static ServiceConfigAccessor getInstance(Context context) {

        synchronized (SLOCK) {

            if (sInstance == null) {

                sInstance = new ServiceConfigAccessorImpl(context);

            }

            return sInstance;

        }

    }



    /**

     * Adds a listener that will be called when server flags related to this class change. The

     * callbacks are delivered on the main looper thread.

     *

     * <p>Note: Only for use by long-lived objects. There is deliberately no associated remove

     * method.

     */

    public void addListener(@NonNull ConfigurationChangeListener listener) {

        mServerFlags.addListener(listener, SERVER_FLAGS_KEYS_TO_WATCH);

    }



    @Override

    @NonNull

    public @Origin int[] getOriginPriorities() {

        int[] serverFlagsValue = mServerFlagsOriginPrioritiesSupplier.get();

        if (serverFlagsValue != null) {

            return serverFlagsValue;

        }



        int[] configValue = mConfigOriginPrioritiesSupplier.get();

        if (configValue != null) {

            return configValue;

        }

        return DEFAULT_AUTOMATIC_TIME_ORIGIN_PRIORITIES;

    }



    @Override

    public int systemClockUpdateThresholdMillis() {

        return mSystemClockUpdateThresholdMillis;

    }



    @Override

    @NonNull

    public Instant autoTimeLowerBound() {

        return mServerFlags.getOptionalInstant(KEY_TIME_DETECTOR_LOWER_BOUND_MILLIS_OVERRIDE)

                .orElse(TIME_LOWER_BOUND_DEFAULT);

    }



    /**

     * A base supplier of an array of time origin integers in priority order.

     * It handles memoization of the result to avoid repeated string parsing when nothing has

     * changed.

     */

    private abstract static class BaseOriginPrioritiesSupplier implements Supplier<@Origin int[]> {

        @GuardedBy("this") @Nullable private String[] mLastPriorityStrings;

        @GuardedBy("this") @Nullable private int[] mLastPriorityInts;



        /** Returns an array of {@code ORIGIN_*} values, or {@code null}. */

        @Override

        @Nullable

        public @Origin int[] get() {

            String[] priorityStrings = lookupPriorityStrings();

            synchronized (this) {

                if (Arrays.equals(mLastPriorityStrings, priorityStrings)) {

                    return mLastPriorityInts;

                }



                int[] priorityInts = null;

                if (priorityStrings != null && priorityStrings.length > 0) {

                    priorityInts = new int[priorityStrings.length];

                    try {

                        for (int i = 0; i < priorityInts.length; i++) {

                            String priorityString = priorityStrings[i];

                            Preconditions.checkArgument(priorityString != null);



                            priorityString = priorityString.trim();

                            priorityInts[i] = TimeDetectorStrategy.stringToOrigin(priorityString);

                        }

                    } catch (IllegalArgumentException e) {

                        // If any strings were bad and they were ignored then the semantics of the

                        // whole list could change, so return null.

                        priorityInts = null;

                    }

                }

                mLastPriorityStrings = priorityStrings;

                mLastPriorityInts = priorityInts;

                return priorityInts;

            }

        }



        @Nullable

        protected abstract String[] lookupPriorityStrings();

    }



    /** Supplies origin priorities from config_autoTimeSourcesPriority. */

    private static class ConfigOriginPrioritiesSupplier extends BaseOriginPrioritiesSupplier {



        @NonNull private final Context mContext;



        private ConfigOriginPrioritiesSupplier(Context context) {

            mContext = Objects.requireNonNull(context);

        }



        @Override

        @Nullable

        protected String[] lookupPriorityStrings() {

            return mContext.getResources().getStringArray(R.array.config_autoTimeSourcesPriority);

        }

    }



    /**

     * Supplies origin priorities from device_config (server flags), see

     * {@link ServerFlags#KEY_TIME_DETECTOR_ORIGIN_PRIORITIES_OVERRIDE}.

     */

    private static class ServerFlagsOriginPrioritiesSupplier extends BaseOriginPrioritiesSupplier {



        @NonNull private final ServerFlags mServerFlags;



        private ServerFlagsOriginPrioritiesSupplier(ServerFlags serverFlags) {

            mServerFlags = Objects.requireNonNull(serverFlags);

        }



        @Override

        @Nullable

        protected String[] lookupPriorityStrings() {

            Optional<String[]> priorityStrings = mServerFlags.getOptionalStringArray(

                    KEY_TIME_DETECTOR_ORIGIN_PRIORITIES_OVERRIDE);

            return priorityStrings.orElse(null);

        }

    }

}

services/core/java/com/android/server/timedetector/TimeDetectorService.java

+1 −1
Original line number Diff line number Diff line
@@ -67,7 +67,7 @@ public final class TimeDetectorService extends ITimeDetectorService.Stub { 
            Handler handler = FgThread.getHandler();



            ServiceConfigAccessor serviceConfigAccessor =

                    ServiceConfigAccessor.getInstance(context);

                    ServiceConfigAccessorImpl.getInstance(context);

            TimeDetectorStrategy timeDetectorStrategy =

                    TimeDetectorStrategyImpl.create(context, handler, serviceConfigAccessor);